Nora Small Cat ™ has her own filing system, of which she is very proud. Actually, she was unhappy when I sealed away my own files, because she had a habit of shredding them to make a little hideaway. So I made her a decoy box of scrap paper, and she’s happy with that, because she can’t read.
I’m happy, because I also dealt with the piles of paper that were spread everywhere around here threatening to overwhelm. Putting them into one big pile, and then sorting that into easy-to-remember (I hope) categories, which then go into their own folders inside the cabinet.